CAN Bus Termination Calculator

CAN Bus (Controller Area Network) is a communication standard used in vehicles and industrial systems to let microcontrollers talk to each other — and proper termination resistors at each end of the bus are critical to prevent signal reflections. Enter your drive voltage, baud rate, cable length, number of nodes, termination type, ambient temperature, and safety factor into the CAN Bus Termination Calculator to get the correct termination resistance. Secondary outputs include minimum power rating, maximum current, bus capacitance, maximum stub length, and the nearest standard resistor value.

V

Supply voltage for CAN transceiver

bps

CAN bus communication speed

m

Total length of CAN bus cable

Total CAN nodes on the network

°C

Operating temperature for power calculations

Power derating factor for reliability

Results

Termination Resistance

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Minimum Power Rating

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Maximum Current

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Bus Capacitance

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Maximum Stub Length

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Standard Resistor Value

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Results Table

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Frequently Asked Questions

What is CAN bus termination and why is it needed?

CAN bus termination prevents signal reflections at the ends of the bus cable. Without proper termination, reflections can cause communication errors and unreliable data transmission. Standard termination uses 120Ω resistors at each end of the bus.

How do I calculate the correct termination resistor value?

For standard CAN buses, use 120Ω resistors at both ends. The total parallel resistance should be 60Ω. For high-speed applications or long cables, consider split termination with additional capacitors for better signal integrity.

What power rating should I use for termination resistors?

Power rating depends on the drive voltage and current through the resistor. Calculate using P = V²/R and apply a safety factor of 2-3x for reliability. Typical values range from 0.25W to 1W for automotive applications.

When should I use split termination instead of standard termination?

Split termination is recommended for high-speed CAN (>500 kbps) or noisy environments. It uses two resistors in series with a capacitor to ground, providing better common-mode noise rejection and EMI performance.

How does cable length affect CAN bus termination?

Longer cables increase capacitance and propagation delay. For cables over 100m, you may need to reduce baud rate or use repeaters. Maximum stub length also decreases with higher baud rates to maintain signal integrity.

What happens if I don't terminate the CAN bus properly?

Improper termination causes signal reflections, voltage level errors, and communication failures. Over-termination (too low resistance) increases current consumption, while under-termination causes signal integrity issues and potential data corruption.

Can I use different termination values for different baud rates?

Standard CAN uses 120Ω termination regardless of baud rate. However, the cable length and stub length limits change with baud rate. Higher baud rates require shorter cables and stubs for reliable operation.